Process gas, particularly in the case of laser welding processing, is fed to a processing zone for machine processing, for example, of a gas nozzle. The process gas can serve mainly to shield a processing point in the processing zone from the ambient air. As an example, by so doing the material melted by the processing beam is prevented from reacting with surrounding air. In this case, the process gas acts as a protective gas, therefore. The protective gas used is an inert gas such as helium, argon or carbon dioxide. Depending on the application, process gas mixtures with several process gases are used also.
But a process gas can also be fed to the processing zone, which is intended to react with the workpiece material and by so doing introduces additional energy into the processing zone. In this case, the process gas serves as a working gas.
Furthermore, a process gas can be fed in addition or as a supplement to the processing zone in order to protect parts of the processing machine from emissions from the processing point. In laser processing, process gases of this type are used, for example, to protect optical elements in the vicinity of the processing point (cross jet gas).
Overall, the process gas feed and, for example, also the resulting removal of the emissions has a decisive effect on the machining process and largely determines the quality of the processing result.
A device for processing workpieces by a laser processing beam is described by DE 38 27 451 C1, which device is characterised by a particularly dynamically controllable process gas feed.
It is known, therefore, from DE 38 24 048 A1, in a method for processing workpieces with a laser processing beam to control the supplied quantity of process gas per unit of time based on the acoustic and optical monitoring of the processing zone. In the previously known method, stored process diagrams are accessed, by means of which desired values for the process gas feed are determined.